The invention relates firstly to a device for developing a latent electrostatic image, situated on a surface, by means of a particulate developer, in which device and image can move relatively with respect to each other and comprising at least developer supply means for the uniform application of developer, a development electrode fitted in an electrically insulated manner and developer removal means, wherein the development electrode comprises several regions which are electrically insulated with respect to each other and means are present to make it possible to supply electrical potentials, independent of each other, to said regions.
Such devices for developing latent electrostatic images are known perse from U.S. Pat. No. 3,908,037. Said publication describes the use of a development electrode which during development moves relatively to a photoconductorsurface on which a latent electrostatic image is present which has to be developed. The development is carried out with use of a dry particulate developer or toner.
The use of a development electrode which is constituted by a plurality of separately energizable regions is said to be particularly useful in case wherein repeated development occurs whereby after each development the developer is transferred to a support surface. By appropriate selection of the voltages of the different regions a cleaning effect may be obtained in which the first regions of the development electrode serve to remove residual toner (regions which precede other regions in order of being faced with a particular area of the latent image), while the later regions act in the actual development.
Such known systems have as a disadvantage that in the developed area's the uniformity in developer density is not optimal in solid and screened area's. At the edges of area's with high developer density further flow phenomena occur; this same effect is considered to be responsible for what is called "Cloudiness" in screenarea's, i.e. a non uniform screen appearance. More over a complete prevention of background developing may not always be obtained. Specially with use of liquid developers or toners afore mentioned drawbacks are even more pronounced.